GB2267314A

GB2267314A - Rotary actuator-operated pretensioner.

Info

Publication number: GB2267314A
Application number: GB9310813A
Authority: GB
Inventors: Mitsuhiko Hiruta; Muneo Nishizawa
Original assignee: Takata Corp
Current assignee: Takata Corp
Priority date: 1992-05-27
Filing date: 1993-05-26
Publication date: 1993-12-01
Also published as: GB9310813D0; ITRM930354A1; SE9301782L; DE4317710A1; IT1261686B; TW242134B; ITRM930354A0; JPH05319212A; SE9301782D0; KR930023220A; FR2691688A1; DE9308032U1

Abstract

A rotary actuator 1 is driven in rotation by pressurized gas supplied by a gas generator 2 and drives a belt take-up reel (R9, Fig 2). A partition wall 112 that separates the pressure section 102A of the operating chamber 102 from the exhaust section 102B receives a seal member 13, which is resiliently urged by a spring 14 into engagement with the body portion (122, Fig 3) of rotor 12. The seal member prevents gas from leaking past the partition wall from the pressure section to the exhaust section. <IMAGE>

Description

2267314 Rotary Actuator-Operated Pretensioner The present invention

relates to a pretensioner for a seat belt system and, in particular, to a pretensioner in which a belt take-up reel is driven in rotation to wind a segment of the seat belt onto it by a rotary actuator operated by gas pressure supplied by a gas generator.

Seat belt pretensioners are often provided in vehicle seat belt systems to tighten the seat belt at the instant of a collision or other emergency and thereby more firmly restrain the seat occupant against being thrown forward. One known type of seat belt pretensioner employs a rotary actuator that is supplied with gas under pressure from a gas generator and is coupled to a belt take-up reel. The gas from the generator is supplied to an annular cylinder chamber of the actuator and drives the rotor in rotation, thereby rotating the take-up shaft. Pretensioners of the type operated by rotary actuators are disclosed in Japanese Patent Publication No. 60-15657 and Japanese Patent Laid-open Publication No. 60-45450.

In previously known pretensioners that are based on rotary actuators as the driving mechanism, leakage of the pressurized gas from the pressure section of the cylinder at various places results in a loss of the available energy of the gas. minimizing the leakage of gas has heretofore been accomplished by maintaining close dimensional tolerances in the manufacture of the components of the actuator. Even with the maintenance of close dimensional tolerances, which increases manufacturing costs, leakage of the gas is still a problem.

Enibodirients of the present inven-Lion desirably provide a pretensioner of the type that uses a rotary actuator that more effectively uses the avail able energy of the gas produced by the gas generator by reducing the loss, which is significant in previously known rotary actuator-operated pretensioners, without requiring close dimensional tolerances to be established and maintained. In this regard, it has been observed that large losses of gas from the pressure section of the annular cylinder chamber occur between the rotor and a is partition wall on the cylinder that, together with the vane of the rotor, defines the pressure section and the exhaust section. In particular, the pressurized gas leaks through a gap between the surface of the partition wall that faces the rotor and the surface of the rotor.

Thus, in accordance with the present invention, there is provided a rotary actuatoroperated pretensioner having a gas generator and a rotary actuator that is driven in rotation by pressurized gas supplied by the gas generator. The rotary actuator has a cylinder that defines an annular operating chamber having side walls, a peripheral wall and a partition wall extending from the peripheral across the operating chamber. The operating chamber receives a rotor having an annular body portion and a vane portion extending across the operating chamber from the body portion and defining, together with the partition wall, a pressure section on one side of the vane portion into which gas from the generator is delivered and an exhaust section on the other side of the vane portion. The cylinder has an exhaust opening to the atmosphere from the exhaust section. The invention is characterized in that a seal member is supported on the partition wall and is resiliently urged into engagement with the body portion of the rotor.

In a preferred embodiment, the invention is further characterized in that the partition wall has a recess opening generally toward the body portion of the rotor, the seal member has a portion movably received in the recess, and a compression spring is received in the recess between a base portion of the recess and the spring.

The seal member interposed between the partition wall and the rotor body prevents gas from leaking through the gap between the rotor body and the end of the partition wall directly into the exhaust section of the operating chamber. Because the exhaust section has a vent hole, though which gas can readily escape to the atmosphere, the exhaust section is at or close to atmospheric pressure. The relatively high pressure differential between the pressure section and the exhaust section and the short length of the gap makes the potential loss of pressurized gas at the gap large. The seal member stops that loss. The resilient urging of the seal member into engagement with the rotor ensures that a good seal is maintained, regardless of variations in the dimensions of the components and small displacements of the rotor relative to the cylinder due to the gas pressure acting on the rotor when the pretensioner is operated.

The invention improves the efficiency of the application of gas pressure on the rotor vane. For a given desired driving force, therefore, a lesser amount of the gas-generating substance can be provided in the gas generator. The size, weight and cost of the actuator can also be reduced, due to the increase in efficiency and reduction of losses. The need for maintaining close dimensional tolerances is also reduced.

For a better understanding of the invention, reference may be made to the following description of an exemplary embodiment, taken in conjunction with the accompanying drawings, of which:

Fig. 1 is a front view of the embodiment with the cover of the cylinder removed, some parts being shown in cross-section; Fig. 2 is a side cross-sectional view of the embodiment; Fig. 3 is an exploded pictorial view of the embodiment; and Figs. 4(A) to 4(D) are front views showing the embodiment at different stages of operation.

As shown in Fig. 1 and Fig 2, the embodiment of a rotary actuatoroperated pretensioner comprises as the driving device for a rotatable belt take-up reel R9 a rotary actuator that is operated by a gas supplied from a gas generator 2. The actuator assembly 1 is attached to one side of a frame Ri of a belt retractor R by screws (not shown). A belt-rewinding spring unit S of the retractor R is mounted on the side of the actuator 1 opposite from the frame R1. Between a take-up shaft R2 of the retractor R and the actuator 1 is an engaging mechanism (described in detail below) for connecting the actuator to the take-up shaft R2 only during operation of the actuator 1. A ratchet wheel R3, which serves as an engaged part of the engaging mechanism, is received on a rectangular portion of the take-up shaft R2 and is, therefore, non-rotatable with respect to the take-up shaft R2.

The actuator 1 comprises a gas supply chamber 101 that receives the gas generator 2, a cylinder 10 having an operating chamber 102 that communicates with the supply chamber 101, and a rotor 12 that is rotatably supported in the cylinder within the operating chamber 102. A vane 121 on the rotor 12, in cooperation with a partition wall 112 on the cylinder 10, separates the operating chamber 102 into a pressure section 102A that communicates with the gas generator and a exhaust section 102B that is open to the atmospheric air. A seal member 13 on the partition wall 122 forms a seal between the partition wall and the rotor 12. The seal member 13 is urged toward the rotor 12 by a resilient loading means, such as a coil spring 14.

Referring next to Fig. 3, the operating chamber 102 of the cylinder 10 has one side open and is bounded by a circular cylindrical peripheral wall and a side wall. The supply chamber 101, similarly, has one side open and is defined by a peripheral wall, a side wall and a wall 103, which is located adjacent to the operating section 102. A cover 10a (Fig. 2) closes the open sides of the chambers 101 and 102. The cylinder has holes for the screws that fasten it to a frame of the retractor. The wall 103, which separates the operating chamber 102 from the supply chamber 101, extends only about one-half of the way across the cylinder, leaving a gap that is filled by a partition wall block 11. A sealing groove 104 is formed on the cylinder 10 around the outer periphery of the operating chamber 102 and the supply chamber 101. An annular flange 105 extends from the side wall of the operating chamber 102 into the operating chamber and surrounds the shaft hole that receives the end portion of the reel shaft R2. An exhaust hole 106 leads from the operating chamber 102 to outside the cylinder 10.

The partition wall block 11 comprises a wall portion 111 that is attached to the flat side of the wall 103 of the supply chamber 101 and extends in a direction traverse to the two chambers 101 and 102, and a partition wall 112 that extends across the operating chamber 102 such that its extremity is close to the surface of the rotor body 122. Sealing grooves 113 and 114 that intersect each other are formed on the end surfaces of the wall portion ill and the partition wall 112 of the block 11. Also, similar sealing grooves 113f and 1141 are formed on the rear side of the partition wall block 11. A gas inlet hole 115 passes is through the wall portion ill, and a notch 116 that receives a portion of the sealing member is provided at the tip of the partition wall 112. A hole (Fig. 1) 117 extends into the partition from the base of the notch 116.

The rotor 12 comprises a body portion in the form of a ring 122 defining within it a space surrounding the outer periphery of a ratchet wheel R3 (Fig. 1 and Fig. 2). The inner surface of the ring 122 also supports the rotor 12 in the cylinder for rotation in the operating chamber, as described below. A vane 121 extends radially across the operating chamber 102 and serves as a pressure-receiving portion on which the gas acts. A bullet guide tube 123 in the form of a rectangular tube is formed on the back of the vane 121 to receive a bullet 15, which is also described below.

An elastomer seal member 16 is mounted on the rotor. The seal member 16 has a wall portion 161 that engages the pressure side of the vane 121, a continuous seal lip 163-on both side edges and end edge, and a frame-like portion 162 that fits over the outer portion of the bullet guide tube 123. When the rotor 12 is rotated, the seal lip.163 serves to seal a gap between the cylinder 10 and the rotor 12 by being forced out against both sides (one of the side surfaces is the side surface of the cover 10a) and at the perimeter of the operating chamber 102 by gas pressure. The upper surface of the portion 162 and a part of the attachment 161 elastically contact a pressure-receiving head 152 of the bullet 15 and serve to seal the opening of the bullet guide tube 123 against leakage.

The bullet 15, which serves as an actuator side engaging means of the engaging mechanism, is received in the opening of the guide tube 123 in such a manner that it can be displaced freely in the radial direction. The bullet 15 comprises the pressure is receiving head 152 for receiving gas pressure and a wedge-like tip 151, which serves as an engaging means with the ratchet wheel R3. The tip 152 is directed toward the ratchet wheel R3.

The seal member 13 comprises a wedge-like body 131 and a guide shaft 132 that is received in the spring accommodation hole. A wedge-like tip of the body 131 serves as a sliding seal that engages the outer peripheral surface of the ring body 122 of the rotor 12.

A pair of bearing rings 17 and 18 rotatably support the rotor 12 on the cylinder 10. The respective bearing rings are fitted to a support flange protruding into the operating chamber 102 of the cylinder 10 and to an annular support flange 191 formed on the cover 10a that covers the open end of the cylinder 10, as shown in Fig. 2, and rotatably support the inner surface of the ring body 122 of the rotor 12.

Therefore, in the assembled state as shown in Fig. 2, the rotor 12 is supported on the outer peripheral surface of the two support flanges 105 and 191 by the two bearing rings 17 and 18.

Two elastomer seals 19a and 19b (Fig. 2), each in the form of an 0-ring, are received, respectively, in each of the sealing grooves 104, 113, 114, 1131 and 114f and serve to seal gaps between the cylinder 10 and the cover 10a, between the supply chamber 101 and the operating chamber 102, and between the pressure section 102A and the exhaust section 102B.

Next, the operation of the above embodiment will be described. Fig. 4(A) shows the configuration of a pretensioner with the above arrangement in the nonoperating position. The rotor 12 is positioned with the bullet guide tube 123 abutting the partition wall 112. Under this condition. the pressure section 102A is at the most compressed state, and the bullet 15 is positioned by suitable means, such as a shear pin, so that it is not engaged with the engagement tooth R31 on the outer periphery of the ratchet wheel R3. Therefore, the take-up shaft R2 is completely separated from the actuator 1, and the retractor may function in its normal manner.

When the gas generator is operated by suitable means, such as an electric signal, gas under pressure is introduced into the pressure section 102A through the supply chamber 101 and the gas inlet hole 115. The force due to the gas pressure acting on the pressurereceiving head 152 of the bullet 15 pushes the bullet inwardly toward the ratchet wheel R3 in the radial direction to the position shown in Fig. 4(B). At this moment, the bullet tip 151 engages a tooth R31 of the ratchet wheel R3, and the rotor 12 is thus engaged with the ratchet wheel R3 by the bullet 15. Accordingly, the take-up shaft R2 is now connected to the actuator 1.

Gas pressure also acts on the vane 121 of the rotor 12, and the force due to the gas pressure acting on the vane causes the rotor 12 to be rotated counterclockwise, as shown by the arrow in Fig. 4(C).

Upon rotation of the rotor, pressure is generated in the exhaust section 102B and is released to atmospheric air through the exhaust hole 106 of the cylinder 10, and the generation of resistance to rotation of the rotor due to a pressure increase in the exhaust section 102B is prevented. Thus, the rotating force of the rotor 12 is transmitted to the take-up shaft R2 through the bullet 15 and the ratchet wheel R3.

Upon the rotation of the take-up shaft R2, a segment of the belt is wound onto the take-up shaft R2, and pretension is imparted by tightening of the belt.

Finally, the rotor 12 reaches the position shown in Fig. 4(D), and the operation of the pretensioner is is completed.

During the operation of the pretensioner, the seal member 13 receives the spring load of the coil spring 14 and is continuously urged against the outer peripheral surface of the ring body 122 of the rotor 12. The seal prevents the gas in the pressure section 102A of the chamber 102 from leaking from the pressure section 102A to the exhaust section 102B through the gap between the tip of the partition wall 112 and the ring unit 122.

Gas leakage through the gaps between both side surfaces of the partition wall 112 and the end wall of the cylinder as well as the cover 10a is blocked by a pair of elastomer seals 19a and 19b engaged in the sealing grooves 114 and 114f. Gas leakage between the vane 121 and the cylinder 10 is blocked by the seal lip 163 of the elastomer seal member 16. Further, leakage from the opening of the bullet guide tube 123 to engagement space is blocked by the engaging unit 162 of the elastomer seal member 16.

Thus, the actuator of the above embodiment effectively stops gas leakage from the pressure section 102A to the exhaust section 102B and from the pressure section 102A to other portions of the actuator. The pressure of the gas generated by the gas generator 2 can be effectively utilized for the operation of the 5 actuator 1 rather than being lost through leakage.

The above-described embodiment of the invention is exemplary, and numerous variations and modifications of the embodiment can be made by those skilled in the art without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention, as set forth in the claims appended hereto.

Claims

Claims 1 1. A rotary actuator-operated pretensioner having a 2 gas generator and a rotary actuator that is driven 3 in rotation by pressurized gas supplied by the gas 4 generator, the rotary actuator including a cylinder having an annular operating chamber 6 having side walls, a peripheral wall and a 7 partition wall extending across the operating 8 chamber, and the rotary actuator having a rotor 9 having an annular body portion rotatably received in the operating chamber and a vane portion 11 extending across the chamber from the body portion 12 and defining with the partition wall a pressure 13 section on one side of the vane portion into which 14 gas from the generator is delivered and an exhaust section on the other side of the vane portion, the 16 cylinder having an exhaust opening to the 17 atmosphere from the exhaust section, characterized 18 in that a seal member is supported on the 19 partition wall and is resiliently urged into engagement with the body portion of the rotor.

1

2. A rotary actuator-operated pretensioner according 2 to claim 1 and further characterized in that the 3 partition wall has a recess opening generally 4 toward the body portion of the rotor, the seal member has a portion movably received in the 6 recess, and a compression spring is received in 7 the recess between a base portion of the recess 8 and the spring.

3. A rotary actuator-operated pretensioner substantially as herein described with reference to, and as illustrated in, the accompanying drawings.